This invention relates to brake booster mechanism and particularly to power assist mechanism for aiding in the manual application of brakes on a vehicle.
It has been proposed in the art to use initial brake pedal movement to actuate a valve control mechanism producing powered force which is transmitted to the braking system before any manual effort is applied to the brakes with an aim to attain to a necessary minimum braking distance of an automotive vehicle.
Several types of power assist mechanism have been developed. These power assist mechanisms have been generally successful and highly efficient in operation, but they usually are of such type that attains the foregoing object by provision of an initial stage of the pedal movement in which the control mechanism is solely actuated without being opposed by any brake reaction force. Difficulties exist, since the first stage is substantially a very short period of time and the corresponding stroke of the pedal and hence an actuating member is also short, so that any manufacturing tolerance tends to cause undesirable non-uniformity of operation of the power assist mechanism. This is considered a drawback particularly for saving substantial manufacturing cost in that, all the components are required to be corrected independently of each other for eliminating their tolerance.
It is a principal object of the present invention to provide an improved power assist mechanism having a simple means for adjusting the initial stage stroke of the pedal and hence the valve control mechanism actuating member so that any manufacturing tolerance of the actuating member can be overcome when the power assist mechanism is installed by adjusting the adjusting means.